Characterization of single cells in tissue samples requires a highly parameterized assay.1 Fluorescence-based flow cytometry (FC) has been the method of choice to study heterogeneous cell populations as it allows for 5-10 parameters to be routinely analyzed.2 However, FC cannot be used for highly parameterized assays (>20 parameters) due to the spectral overlap of the fluorophores used for analyte detection.3 A solution to this problem is to substitute the optical detection and fluorescently tagged antibodies in FC, for mass detection with an inductively-coupled plasma spectrometer (ICP-MS) and isotope-tagged antibodies. This technology, known as mass cytometry (MC), is capable of detecting numerous bioorthogonal isotopes (theoretically >100) with single mass unit resolution over multiple orders of magnitude.1 MC allows experiments analogous to flow cytometry but with significantly greater parameterization. MC has been used to detect and quantify 34 cellular parameters simultaneously to reveal the drug response across a human hematopoietic continuum.4 
MC experiments can be done by using commercially available MaxPar© to label antibodies with metal chelating polymers that bind a range of high molecular weight metal isotopes, usually lanthanides. Element tags attached to polymer backbones are described in U.S. Pat. No. 9,012,239. Specific examples disclosed include elemental tags comprising the metal chelating groups diethylenetriaminepentaacetate (DTPA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA).
Other mass tagged reagents are desirable.
The first organotellurium compound was synthesized by Wöhler in 1840.6 Increasingly organotellurium compounds are being investigated in living systems, although this area of research remains underdeveloped.7,8 Tellurium has no known biological role in prokaryotic or eukaryotic cells. In biological systems, tellurium metabolism is poorly understood, however it is presumed to follow the metabolic pathway of its analogue, selenium. Microorganisms have been found to methylate inorganic tellurium to volatile or ionic species for excretion. Experimental evidence of this process is scarce due to the instability of the metabolites7. However the number reports of cellular studies involving aryl, vinylic, alkynyl and alkyl telluroethers in biological systems are increasing.9-14 The majority of this research has been based upon the ability of aryl telluroethers to mimic glutathione peroxidase activity providing, in some cases, resistance to oxidative stress and in other case disregulating redox homeostatsis leading to appoptosis.15,16 Recent murine studies have shown diverse effects from the expected toxicity of an amino acid based aryl telluroether to increased memory in mice treated with an alkyl telluroether.17,18 